The compound 2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone, hereinafter referred to by the common name "clomazone", is a potent herbicide as evidenced by its ability to control, for full growing seasons and at low application rates in soybean stands, a broad spectrum of grasses and broadleaf weeds that compete with soybeans. As with many herbicides, however, clomazone is not as quickly metabolized by some crops, trees and ornamentals as it is by soybeans. Such intolerance can result temporarily in unsightly yellowing or whitening of the plants unless precautions are taken to prevent or minimize exposure. These precautions include control of surface spraying to forestall drift to adjacent fields planted with low tolerance crops, incorporation into soil during tillage to avoid volatilization due to high temperature and/or moisture, rotation to sensitive crops after specified periods of time following application of clomazone, and thorough cleaning of spray tanks to avoid contaminating other chemicals.
Although good agronomy dictates use of one or more of the foregoing practices at all times, it will be evident that measures that will permit reduction in rates of application of clomazone or which otherwise will increase the tolerance of desirable plants to clomazone without substantial diminution of herbicidal efficacy against weeds, will greatly expand the usefulness of clomazone and ultimately result in lower cost. For example, because corn is sensitive to clomazone, clomazone cannot be used to combat weeds in corn stands. To prevent carryover, fields treated with clomazone cannot be rotated to corn for at least nine months after application of clomazone. Other gramineous crops are similarly disadvantaged.
In this specification the term "crops" includes not only agronomic crops but plants of all kinds, and the term "gramineous" includes both cereal and non-cereal grassy crops, such as corn, wheat, oats, barley, rice, cotton, sorghum and sugar cane.